There is provided an erasing technique capable of erasing an erasable image printed on a sheet by heating. By this erasing technique, a sheet can be reused by erasing an erasable image on the sheet.
A sheet (hereinafter, referred to as an “erased sheet”) for which the erasing process is completed by erasing an erasable image in an erasing device which erases the erasable image is reused in a printer or the like, and thus it is necessary to detect presence or absence of residues after erasure in advance.
In addition, the erased sheet is different from an unused sheet, thus appearance defects such as wrinkles occur, and when reused, it is necessary to detect such an appearance defect in advance.
In the erasing device, if a printing image erasing unit which erases an erasable image and a stacking portion which stacks the erased sheets thereon are integrally formed, the erased sheets can be automatically stacked in the stacking unit.
In such a case, if residual images on the erased sheet and the appearance defect of the erased sheet can be automatically detected and then whether or not to reuse the sheet can be determined, the erased sheets stacked in the stacking portion can be reused without concern. If the erased sheets can be sorted according to their sizes in the stacking portion, the stacked erased sheets can be easily treated.
In addition, in a case where the erased sheet is used in an image forming device such as a printer, if whether or not to reuse the sheets can be determined using functions of a corresponding image forming device before a plurality of erased sheets are contained in a paper feeding cassette or the like, the erased sheets can be reused without concern.